In 1992, childhood friend and investment banker John W. Rogers, Jr., appointed Duncan director of the Ariel Education Initiative, a program mentoring children at one of the city's worst-performing elementary schools and then assisting them as they proceeded further in the education system.[2] After the school closed in 1996, Duncan and Rogers were instrumental in re-opening it as a charter school, Ariel Community Academy.[3] In 1999, Duncan was appointed Deputy Chief of Staff for former Chicago Public Schools CEO Paul Vallas.[4]

Mayor Richard M. Daley appointed Duncan to serve as Chief Executive Officer of the Chicago Public Schools on June 26, 2001.[5] Opinions vary on Duncan's success as CEO; one prominent publication notes improved test scores and describes Duncan as a consensus builder,[6] while another finds the improvements largely a myth and is troubled by the closing of neighborhood schools and their replacement by charter schools, and what it describes as schools' militarization.[7]

Duncan was appointed U.S. Secretary of Education by President Barack Obama and confirmed by the Senate on January 20, 2009.[8] One of Duncan's initiatives as secretary has been a $4 billion Race to the Top competition. It asks states to vie for federal education dollars by submitting proposals that include reforms such as expanding charter schools and judging teachers partly on how well their students do on standardized tests.[9] Duncan and Agriculture SecretaryTom Vilsack are the most senior members of the Obama cabinet, having served since 2009.

In March 2011, Duncan said 82 percent of the nation’s public schools could be failing by next year under the standards of the No Child Left Behind law. The projection amounts to a startling spike from current data, which shows that 37 percent of schools are on track to miss targets set by the law. "Four out of five schools in America would not meet their goals under [No Child Left Behind] by next year", Duncan said in his opening statement.

On July 4, 2014, the National Education Association, the largest teacher's union in the United States, passed a resolution of "no confidence" in Duncan's leadership of the Department of Education and asked for his resignation.[10]

On July 13, 2014, the American Federation of Teachers approved a resolution calling for Education Secretary Arne Duncan to resign if he does not improve under a plan to be implemented by President Barack Obama.[11] The “improvement plan” would require that Secretary Duncan enact the equity and funding recommendations of the Equity Commission’s “Each and Every Child” report; revise the No Child Left Behind and Race To The Top “test-and-punish” system of accountability to a “support-and-improve” structure; and “promote rather than question” teachers and school staff.

On May 11, 2014, Duncan was a member of the 2014 USA Basketball 3x3 Men's Championship Team. The team of Duncan, Jitim Young, Thomas Darrow and Craig Moore qualified to represent the United States in Moscow, Russia in the 24-country 2014 FIBA 3x3 World Championship from June 5–8.[20] Duncan's schedule did not permit him to attend,[21] but the team finished in 9th place in the 24-team tournament.[22]

Addressing a group of school superintendents in late 2013, Arne Duncan stated that he found it "fascinating" that some of the opposition to the Common Core State Standards Initiative came from "white suburban moms who — all of the sudden — their child isn't as brilliant as they thought they were, and their school isn't as good as they thought they were."[23] This had sparked outrage among different facets of society, ranging from the "white suburban mom who feel marginalized and misunderstood", the "non-white parent who wants to know why everyone is only now so upset", to the "non-white parent who wants Arne Duncan to know that she (or he) hates the Common Core, too".[24]

Vice-President of Content with HBCU Buzz Inc., Robert K. Hoggard wrote in his open letter to Duncan, "Shockingly, over 14,000 students from our nation’s HBCUs have been declined Parent PLUS loans. As of Aug. 9, 300 students from Morgan State University were in jeopardy of dropping out because of lack of financial aid. The Education Department recently dropped the maximum income eligibility for Pell Grants to $28,000, making thousands of urban applicants ineligible. It is an injustice for thousands of students and someone like myself with a 3.3 GPA to be declined from federal aid to pay for school. What will you do for the thousands of students who are faced with a conundrum like this?" [25]